Acoustical testing systems are known which provide calibrated sound pressure levels and frequencies. These are preferably designed to drive the device under test in an anechoic environment, i.e., free of sound reflections. Typically, this type of environment is impractical for small testing systems, especially at the low audio frequencies. The output of the device under test is then passed through a measuring system which is capable of providing readings of sound pressure level and/or harmonic distortion components. A significant drawback of these existing acoustical testing systems is that a highly-skilled operator is required for their proper operation due to their requirement for complicated interconnection of parts of the system combined with easily misinterpreted readout means. They generally use thermionic components with their attendant problems regarding long term stability, power consumption and size.
The present acoustical testing system eliminates many chances for operator error by minimizing the number of necessary interconnections of parts and further provides digital readout means which, when coupled with automatically adjusted and scaled circuitry, allows only positive reading of the performances of the devices to be tested. Solid state circuitry is utilized which provides excellent long term stability, low power consumption and small size.
An object of the present invention is to provide an acoustical testing system which overcomes the drawbacks of existing systems and minimizes operator error by eliminating a number of interconnections of parts that were necessary in such existing systems.
Another object of the present invention is the provision of an acoustical testing system that utilizes digital readout means to provide accurate readings of the performances of a device under test.
A further object of the present invention is to provide an acoustical testing system having automatically adjusted and scaled circuitry which provides positive information to be processed thereby.
An additional object of the present invention is the provision of a Wien bridge oscillator circuit which provides a sinusoidal wave of low distortion and of a well-definded amplitude.
A still further object of the present invention is to provide an analog to digital converter circuit that provides logarithmetic conversion of an input signal as well as providing linear amplification of such input signal for distortion analysis processing.
Still an additional object of the present invention is the provision of an automatic voltage control circuit which provides a stabilized amplitude of output signal which is a close reproduction of the input signal thereto.
A still another object of the present invention is to provide a dual slope integrator circuit of simplified construction which performs an analog to digital conversion as well as providing clock signals to other digital circuitry.
These and other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings. It is to be understood that variations of the present invention can be made without departing from the scope of the invention as defined herein.